<p>Phase redistribution is a complicated physical phenomenon which occurs in dividing two-phase flow in T-junctions. In this study detailed experimental data of phase redistribution and associated pressure changes in T-junctions having horizontal inlet are presented for both annular and stratified inlet flows. Two phenomenological phase redistribution models for annular and stratified flows were developed. The objectives of the study are enriching the available data bank on the subject through the experimental measurements and enhancing current understanding of the phenomenon through model development and analysis.</p> <p>Two-phase redistribution in T-junctions was found to be significantly affected by the inlet flow conditions, i.e. inlet flow pattern, inlet quality and inlet flow rates. The phase redistribution phenomenon also depends on the junction geometry, i.e. branch orientation and diameter. The experimental results showed that for annular flow in horizontal T-junctions an increase of inlet quality reduces the degree of phase redistribution while the inlet mass flux was found to be less significant. However, in stratified flow the increase of either the inlet superficial vapour or liquid velocities increases the degree of phase separation. The experimental results also showed that decreasing the branch diameter will increase the degree of phase separation. Moreover, downward orientation of the branch can reduce the branch flow quality significantly.</p> <p>The pressure changes in T-junctions were correlated using simple momentum and energy balances for the run and branch respectively using measured void fractions. The run momentum correction factor was found to be independent of inlet flow conditions but was dependent on the junction geometry. The branch two-phase multiplier was found to depend on both the inlet flow conditions and junction geometry. Comparison of the present data on pressure changes in T-junctions with some available models showed that those models which account for phase redistribution effects were better than the others in correlating the present data, confirming the strong interdependence between the pressure changes and phase redistribution.</p> <p>A general phenomenological phase redistribution model was derived based on the analysis of available models. This general model was extended to two phenomenological models for annular flow and stratified inlet flows. Each of the models included two submodels to account for two phase distribution in the inlet tube and phase redistribution in the junction. Comparisons of the present experimental data and some available models were made and the results indicate that most of the available models can predict 70% of annular flow data and 80%of stratified flow data within +40%of the measurements. The newly developed models in this study can predict 90% of the data within +40% for both annular and stratified flows.</p> / Doctor of Philosophy (PhD)

<p>Excitation of lightly damped drive system resonances severely limits the performance of most current robotic manipulators. Also, many industrial applications require the control of the contact forces in order to execute contact tasks properly. This dissertation discusses the development and experimental verification of advanced high performance control algorithms in order to control the position and contact force of nonlinear manipulators with flexibilities which reside in the drive systems. An experimental two-link planar manipulator has been designed and constructed to test the control algorithms. The developed manipulator exhibits damped drive system resonances and highly nonlinear and coupled dynamics.</p> <p>Several techniques for controlling the position and force of flexible joint robot manipulators are developed and evaluated. A collocated Proportional-Derivative controller is implemented to demonstrate the limitation of such a controller which is commonly used for industrial robots. Then, a fourth order feedback linearizable model is constructed and analyzed. A feedback linearization controller is designed, simulated and implemented in the joint space as a preliminary investigation of the feedback linearization performance. Results proved a tracking performance superior to that of the PD controller and support applying feedback techniques for position and force control.</p> <p>Two model-based position and force control approaches based on feedback linearization concept are developed, simulated and implemented. The dynamic hybrid controller deals with the contact with rigid environments while the impedance control deals with performing free and/or contact with compliant environment motions. The results indicate excellent performance in tracking the position and regulating the contact force. These two approaches serve as basic structure for the design of robust and adaptive controllers.</p> <p>A robust sliding mode controller is designed, simulated and implemented to maintain the model-based tracking performance in the presence of payload variations and other parametric uncertainty. The problem is formulated by using the feedback linearizable model and the constraint imposed by the contact environment, to characterize the disturbance caused by parametric uncertainty in the system. In addition, the effect of parametric uncertainty on computing the unmeasured state elements is included in the analysis and the design of the robust controller. Results indicate that the controller obtains an excellent tracking performance in the presence of parametric uncertainty. This controller solves the problem of the necessity of the exact state of the feedback linearizable system for feedback. In addition, a specific relation between the uncertainty bounds and the achievable accuracy is derived. Another alternative to deal with parametric uncertainty is an adaptive cascade controller which is developed, simulated and implemented. It consists of a direct adaptive controller for the rigid dynamics and a Model Reference Adaptive Controller (MRAC) for the flexible dynamics. Results indicate good force tracking with slow position response. The cascade approach requires extremely fast actuator to achieve the feedback linearization results. A robust sliding mode observer is developed in order to estimate the unmeasured state elements of the feedback linearizable system in case of parametric uncertainty. This observer is useful for the successful application of adaptive feedback linearization algorithms. An adaptive feedback linearization control algorithm combined with the sliding mode observer is developed and simulated. The formulation enables designing adaptive laws using the original system state and the angular accelerations instead of the state of the feedback linearizable system and characterizing the stability of the overall system. The simulation results show the ability of the control algorithm to achieve position and force tracking by robust estimation of the state vector and updating of the robot parameters.</p> / Doctor of Philosophy (PhD)

<p>Efficient scheduling in discrete manufacturing environment can improve productivity through reduced work-in-progress and finished good inventories. This research examined the feasibility and advantages of using genetic algorithms in manufacturing scheduling. All literature to date indicate that there is a need for better scheduling algorithms which can provide better and faster solutions. This thesis focuses on the improvement of the scheduling performance through: a) the application of genetic algorithms to the schedule optimization problem, b) the consideration of batch splitting and c) dynamic scheduling.</p> <p>First, genetic algorithms are developed for two types of scheduling situations: a) scheduling in the presence of single process plans without any routing flexibility and b) scheduling where routing flexibility and multiple process plans exist. Analytical techniques and heuristics-based methods have been developed by other researchers to solve such scheduling problems which are useful for limited size problems. Since the schedule population size is fixed in genetic algorithms, there is a tremendous reduction in the memory requirements. In every generation bad schedules are replaced by better ones. Also, since genetic algorithms performs a multi-point search at a time, they are relatively faster than other techniques used for scheduling which are usually based on single point search. Genetic algorithms models were formulated and tested using nineteen example problems for both flexible and fixed routing scenarios. Numerical results show that the genetic algorithms approach perform significantly better than other approaches both in terms of funding the optimal/near optimal solution and the computation time. The saving in computation time was up to 50% in some cases. Because of the vast number of schedules available in the case of multiple process plans, dispatching rules have been employed in the genetic algorithms to obtain a satisfactory schedule. It is often observed that in the case of alternate routings and while using dispatching rules, researchers tended to use a single job in each order which is rarely the case in practice. In this thesis, both alternate routings and order sizes greater than one are simultaneously considered along with dispatching rules while scheduling with genetic algorithms. Twelve different dispatching rules and seven performance criteria are used and the performance of each rule has been studied extensively with respect to each of the performance criteria.</p> <p>Second, three new batch splitting policies were introduced in this research to split the batches into smaller sub-batches. A process plan-based method was developed, where the information available from the process plans is used for batch splitting. This is different from other batching policies where batching is done based on inventory models from queueing theory for which cost function consisting of ordering, inventory holding and work-in-process carrying costs are required. The new batch splitting policies were compared with existing ones and the results show that in several cases the newly developed policies performed significantly better than existing ones. The improvement in the performance was observed to be in the range of 35% to 45%.</p> <p>Next, the dynamic scheduling aspects are considered and rescheduling algorithms were developed for four kinds of uncertainties. These include unexpected machine breakdown, rush order arrival, order cancellation and increased order priority. These algorithms reschedule only interrupted tasks, hence focusing on local rescheduling. These algorithms were tested using three different performance criteria namely, mean flow time, mean tardiness, and average machine utilization. The developed rescheduling algorithms proved successful in dealing with the shop floor uncertainties and the results indicate that the proposed algorithms are effective and could easily be used to dynamically schedule the manufacturing systems in the presence of disturbances.</p> <p>Finally, as part of the system implementation, a user interface has been developed in 'C' to input required scheduling data used for schedule optimization. The scheduler outputs a list of several good schedules. These schedules are then analyzed by the output analyzer which outputs a list of different performance criteria values, machine utilizations, ready and completion times of each order and the Gantt chart of the best schedule.</p> / Doctor of Philosophy (PhD)

<p>The increase in quality requirements demands efficient integration of design and manufacturing concerns. This thesis develops a robust design procedure and a novel experimental optimization approach for considering manufacturing tolerances (dimensional and geometric) from both design and manufacturing perspectives. Manufacturing capabilities prohibit the tight control of variations in geometry, dimensions and positions in system components. Two formulations are used where manufacturing tolerances are considered as: i) control variables and ii) noise variables beyond the designer's control. Results indicate the superiority of the developed procedure to detect a design region where system response is robust to sources of variations. Moreover, the procedure overcomes the shortcoming of on-line programming to deal with multi-variable problems and multi-level noisy space. The procedure is applied efficiently and successfully to typical product and process design.</p> <p>A statistical optimization procedure is developed, implemented and tested to deal with situations where there is no explicit objective functions. The procedure results in a robust design by proper assignment of nominal and tolerance values. Standard matrix decomposition methods and orthogonal search allow obtaining functionally independent designs. The developed procedure and techniques change design specifications from 'acceptable within limits' to 'close-to-target value'. This technique has the advantage of reducing the tolerance optimization problem and minimizing manufacturing costs.</p> <p>The concept of orthogonal arrays and experimental optimization is used to develop an algorithm for unconstrained and constrained discrete problems. The algorithm employs specially coded designs to form combinatoric search in one and two domains. As a search in one domain, the algorithm uses data from Coordinate Measuring Machines (CMMs) and evaluates the tolerance zones of engineering features such as straightness and roundness (2-Dimensional) and flatness, cylindricity and sphericity (3-Dimensional). The problem of least cost tolerance allocation and optimum process selection is formulated as a discrete optimization problem. The problem is viewed as a search in two domains: the first is tolerance allocation that satisfies the assembly functional requirement; the second is process-selection such that the production cost is minimal. This formulation is based on coupling an inner array (tolerance selection domain) and an outer array (process selection domain). The choice of different structures of orthogonal arrays has a tremendous impact on the resulting minimum production cost and optimum tolerances. Each orthogonal array can be represented by a search graph which can aid the designer in the initial assignment phase. The developed algorithm overcomes one major shortcoming of almost all existing search techniques namely the need for excessive number of function evaluations and provides near-to-global optimum consistently with high reliability.</p> <p>Finally, the experimental design techniques are used to deal with the problem of linear and nonlinear tolerance analysis of mechanical assemblies. The principal goal was to find a substitute for the expensive Monte Carlo-based simulation technique. Results illustrate the successful application of different orthogonal arrays in yielding a comparable system moments in small finite number of experiments with a sample of 10,000 (linear assembly) and 1,000 (nonlinear assembly).</p> <p>This dissertation surveys the literature and offers solutions to various design and manufacturing problems. In fact, it proposes unique tools and techniques to tackle problems such as robust product and process design, nominal and tolerance value assignment, form tolerance evaluation, discrete optimization and linear and nonlinear tolerance analysis.</p> / Doctor of Philosophy (PhD)

<p>The boundary layer equations governing the conservation of mass and momentum and the corresponding boundary conditions are derived, using spherical coordinates for flow past a rotating sphere. A finite-volume-based numerical scheme using structured orthogonal body-fitted grids was used to examine potential and vortex flow around a stationary sphere and flow fields around rotating spheres whose axes are parallel and perpendicular to the free stream direction. Some parametric studies were conducted. The results are presented in graphical form for flow visualization. Experiments for the case of the rotational axis being perpendicular to the free stream were designed and data generated using a triple-sensor probe. It has found that the numerical results agreed reasonably well with experimental results within experimental uncertainty. The comparisons were not completed over whole flow field due to the limitations in the experimental conditions.</p> / Doctor of Philosophy (PhD)

<p>Plastics recycling has received significant attention within the past decade. Positive or negative, the attention has provided an impetus for the plastics industry to advance recycling technology. High density polyethylene blow molding resins have been identified as a primary material for solid waste minimization and recycling. This thesis is concerned with the effects of multiple extrusion passes on the processing and product application properties of high density polyethylene blow moulding resins. The objective is to provide a comprehensive analysis on the system of properties as they are affected by multiple extrusion passes.</p> <p>A justification for this present work is provided by a description of the current state of plastics recycling in terms of the history, legislation and technology. The role of political and global market pressures, relative to legislative initiatives such as the Green Dot program in Germany, the 3 R's legislation in Ontario, the content legislation in California and the decision to ban products such as polystyrene foam clamshell packaging, and the impact of these events on the research initiatives in plastics recycling is discussed.</p> <p>An experimental study into the effect of multiple extrusion cycles on the properties of a virgin homopolymer, virgin copolymer, natural post consumer and mixed colour post consumer blow moulding resin was conducted. Rheological properties such as shear and elongational viscosity and elastic modulus were studied in the context of changes experienced during recycling. The G' - Gil (elastic storage and loss modulus) crossover point was used to measure relative changes in the polydispersity index and molecular weight distribution. It is also shown how parameters such as the Bagley correction factor, extrudate swell and sag are sensitive to the effect of multiple extrusion passes. Strength properties such as tensile strength and environmental stress crack resistance were measured. A rationale for the significant decrease in the environmental stress crack resistance of the virgin copolymer resin is presented. The results are analyzed in terms of known degradation mechanisms such as chain scission and cross-linking, and their relationship to the Phillips and Ziegler-Natta catalyst systems. Principal component analysis, a multivariate statistical technique, was applied to this plastics recycling study to provide data based support in the identification of those responses, within a system of correlated responses, which are most affected by multiple extrusion passes.</p> / Doctor of Philosophy (PhD)

<p>The thesis investigates roll turning for the maintenance of steel mill rolls at DOFASCO and culminates in the specification of a roll turning lathe. The thesis can basically be divided into three main categories: (1) The application of steel mill rolls for both hot and cold rolling processes, their requirements and characteristics.</p> <p>(2) Present roll maintenance practices and machinery. All rolling mill rolls require a regular redressing to restore the specified surface quality and the specified cylindricity which is necessary to produce a high quality product. Roll surface conditions prior to machining are of particular interest. A new approach to the maintenance of steel mill rolls is investigated. This is the replacement of roll grinding, which is generally applied throughout the steel industry, by roll turning.</p> <p>(3) The economic justification for roll turning leads to the development of specifications for the selection and procurement of a roll turning lather for the maintenance of steel mills rolls at DOFASCO.</p> / Master of Engineering (ME)

<p>Modern heat-exchangers are susceptible to damage due to the excessive tube vibrations caused by the shell side fluid flow. The present investigations seeks to further the understanding of flow induced vibrations due to fluid-elastic instability in tube arrays.</p> <p>A low-speed wind-tunnel having 305 x 305 mm, working-section, was used to conduct the experiments. The tube-array was a parallel-triangle having a pitch/diameter = 1.375. The array was 18 rows deep with 5 tubes in each row. Nineteen elastically mounted movable tubes in the front of the array were especially designed so that natural frequency and damping could be controlled precisely over a wide range of values. Positions for as many as nine rows of fixed tubes in the front of the tube-array were available in order to facilitate studying the effect of tube-bundle size on tube response.</p> <p>The experiments have indicated that the first tubes to become unstable in a particular tube-bundle are in the first few rows, and that the third and fourth rows are the critical ones. From the fluid dynamic damping-flow velocity results obtained for the array tested, it suggests the use of the static damping measured in still fluid for the estimate of the velocity for the onset of instability. For the first time a fluidelastic stability boundary as a function of the mass ratio has been determined experimentally for the array. This result along with the result obtained by Grover for the fluidelastic stability boundary as a function of the damping only, show that the mass ratio and the damping behave independently of each other, i.e., they should not be lumped together in the damping factor.</p> / Master of Engineering (ME)

<p>The ability to predict, measure and control the geometric accuracy of the machining process has become of significant importance to industry in its pursuit of successful competition in today's market place. This thesis describes the development and integration of the different subsystems required for the implementation of geometric adaptive control in bar turning. These subsystems include modeling of the machining system, on-line measurement of the workpiece geometry, tool actuation and predictive control design.</p> <p>A mechanistic dynamic model of the machining system in bar turning is developed. The model accounts for the rather complex geometry of a multi-edged cutting tool and considers the dynamics of both the tool and workpiece. Also, the simulation of machining dynamics is significantly enhanced by incorporating a mechanistic ploughing force model which accounts for process damping. The model enables the simulation of the process for a wide range of cutting conditions and the prediction of cutting forces, workpiece accuracy and machined surface topography. The model predictions are verified using experimental results of turning hardened steel using ceramic inserts.</p> <p>A novel non-contact sensor is then developed for on-line high speed monitoring of the workpiece diameter while using a cutting fluid. The measurement system employs three ultrasonic transducers and provides an absolute diameter measurement. An algorithm based on multi-probe measurements is developed to process the radius data and simultaneously compensate for sensor misalignment by tracking the center-line of the workpiece. The system is incorporated into a CNC lathe and provides an accuracy of±5 μm within a working range of 20 mm. The accuracy and repeatability of the measuring system are tested experimentally under realistic cutting conditions. The applicability of the measurement system to provide complete on-line assessment of workpiece geometry is also demonstrated by evaluating the workpiece geometrical tolerances. The influence of different parameters such as fitting objective functions, size of data sets, and data conditioning on such strategy are investigated.</p> <p>A model-based predictive controller is designed and implemented to minimize the form error of the workpiece in bar turning. The mechanistic model of the machining system is simplified and reformulated into the state space to permit design and real-time implementation of the control system. The measurement system is set as close as possible to the cutting edge (at a distance of 0.27 mm). An optimal regulator with a Kalman Filter is designed. The on-line measurement of the workpiece diameter is used through the Kalman filter to update the model predictions with unmodeled process disturbances such as tool wear and thermal deflections of the tooling system. The system is implemented on a CNC lathe retrofitted with an Open Architecture Controller. The output of the geometric controller is used to govern the position of the tool tip in real-time by commanding the same servo motor which is driven by the preprogrammed G-code. The control system is tested experimentally under different cutting conditions and is found to provide a significant improvement of more than 90% in workpiece geometric accuracy.</p> / Doctor of Philosophy (PhD)

<p>The behaviour of a centrifugal volute pump as a source of pressure pulsations as well as the role that the pump-pipeline interaction plays in the amplification of these pressure pulsations were experimentally investigated.</p> <p>A test apparatus was designed and built which features acoustic tuning by pump shaft speed control, dynamic pressure measurements at different locations of the system and qualitative flow visualization capabilities.</p> <p>A semi-empirical model based on a combination of a Green's function solution for the one-dimensional acoustic boundary value problem and a decay function, corresponding to the break down of large cortex structures in the cascade of turbulence, was developed to separate pressure pulsations of acoustic and hydraulic nature.</p> <p>Flow visualization in the acoustic near field around the pump's cut-water region was correlated with the acoustic pressure pulsations. A study, parametric in Helmholtz number, relative pump flow rate and cut-water tip radius, was conducted.</p> <p>Results pertain to the acoustic behaviour of a pump in a piping system:</p> <p>The pump acts primarily as a pressure source that may be acoustically reflective or transparent depending on the prevailing flow conditions. The near field shows pulsing flow separation which occurs on either side of the cut -water depending on relative flow rate. For cut-water geometries with a clear separation point (sharp tip), a strong sound generation dependence on the relative flow is displayed. A well defined point of flow separation at the cut-water tip leads to the largest separation region and also the largest acoustic pressure pulsations. Rounding the cut-water has the effect to permit motion of the stagnation point, thereby reducing the size of the separation region as well as the acoustic pressure pulsations. Clearly, the geometrical details of the cut-water region play a significant role for sound generation without obvious changes in hydraulic performance.</p> / Doctor of Philosophy (PhD)